Because of the recent concern about electric power shortages and need for global environmental protection, households, shops, buildings, etc. (hereafter referred to as “power consumer's facilities”) have been required to save power. In particular, demands for electric power increase in the summer and in the winter, and the power consumption in each power consumer's facility may exceed contract power agreed upon with an electric power company. To effectively save power so that the power consumption does not exceed the contract power, the technique of controlling, by a power control device (e.g. energy management system (EMS)) installed in each power consumer's facility, load apparatuses, dispersed power sources, or the like in the power consumer's facility has been known. In a conventional power control device, the power consumption of each load apparatus is detected by a power sensor, and sensor data acquired by the detection is transmitted to a server or the like. The server or the like transmits a control signal according to the power consumption of each load apparatus while monitoring the power consumption, so that the power consumption of each load apparatus is efficiently reduced.
Consider the case where, when the power control device stops as a result of interruption of power supply due to a power failure or the like and later recovers from the power failure, the power control device stores data in a nonvolatile storage medium. In this case, if the process includes such control that charges a capacitor to prepare for another power failure, the start of the power control device delays and the power control device is not functional, as a result of which the power consumption may exceed the contract power with the electric power company.
In view of this, it has been conventionally proposed to connect any apparatus that is not allowed to stop operation due to a power failure, to an uninterruptible power supply (UPS) (for example, Patent Literature (PTL) 1). With the technique of PTL 1, when power fails, the UPS supplies power and, while power is being supplied from the UPS, apparatuses lower in priority are stopped, thus preventing the power control device from stopping due to the power failure.